ERROR Error: StaticInjectorError[CervejaService]:
  StaticInjectorError[CervejaService]:
    NullInjectorError: No provider for CervejaService!
    at _NullInjector.get (core.js:993)
    at resolveToken (core.js:1281)
    at tryResolveToken (core.js:1223)
    at StaticInjector.get (core.js:1094)
    at resolveToken (core.js:1281)
    at tryResolveToken (core.js:1223)
    at StaticInjector.get (core.js:1094)
    at resolveNgModuleDep (core.js:10878)
    at NgModuleRef_.get (core.js:12110)
    at resolveDep (core.js:12608)

import { Cerveja } from './../core/model';
import { Injectable } from '@angular/core';
import { Http } from '@angular/http';

@Injectable()
export class CervejaService {

  cervejasUrl = 'http://localhost:8080/cervejas';

  constructor(private http: Http) { }

  adicionar(cerveja: Cerveja): Promise<Cerveja> {
        return this.http.post(this.cervejasUrl,
        JSON.stringify(cerveja))
      .toPromise()
      .then(response =>  response.json());
  }
}